Fellow with principles defects (5)
I believe the answer is:
flaws
'defects' is the definition.
('flaw' can be a synonym of 'defect')
'fellow with principles' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'with' is a charade indicator (letters next to each other).
'principles' becomes 'laws' (I can't explain this - if you can you should give a lot more credence to this answer).
'f'+'laws'='FLAWS'
Can you help me to learn more?
(Other definitions for flaws that I've seen before include "weaknesses" , "Defects" .)